Immune responses are necessary for protection against potentially pathogenic microorganisms. However, undesired immune activation can cause injurious processes leading to damage or destruction of one's own tissues. Undesired immune activation occurs, for example, in autoimmune diseases where antibodies and/or T lymphocytes react with self antigens to the detriment of the body's tissues. This is also the case in allergic reactions characterized by an exaggerated immune response to certain environmental matters and which may result in inflammatory responses leading to tissue destruction. This is also the case in rejection of transplanted organs which is significantly mediated by alloreactive T cells present in the host which recognize donor alloantigens or xenoantigens.
Immune tolerance is the acquired lack of specific immune responsiveness to an antigen to which an immune response would normally occur. Typically, to induce tolerance, there must be an exposure to a tolerizing antigen, which results in the death or functional inactivation of certain lymphocytes. This process generally accounts for tolerance to self antigens, or self-tolerance. Immunosuppressive agents are useful in prevention or reduction of undesired immune responses, e.g., in treating patients with autoimmune diseases or with allogeneic transplants. However, immunosuppressive agents can also cause systemic immune suppression, toxicity and even death due to opportunistic infections.
There is a need in the art for safer and more effective means for inducing immune tolerance, especially antigen-specific immune tolerance. The instant invention addresses this and other needs.